Fireplace Secondary Burn

[cmk8895]

Hi everyone. Long time lurker, but just registered so I can post.

I am well aware of the value prop of an insert or even a stove installed into my "regular" masonry fireplace. But, I'm an Engineer and a thinker, so I just have to know about weird ways to do things. haha

I have learned about secondary burn as well as catalytic burns for higher burn efficiency / lower exhaust particulates. I got to thinking about if secondary air injection into a fireplace is possible for a secondary burn. I find a TON of info on air injection at the fire, but almost nothing about a secondary burn above the fire in a traditional fireplace. (I believe that getting all the exhaust gasses to pass through a cat would be nearly impossible, so not really thinking about that, but if you have ideas....)

The only thing that I can find even mentioning secondary burn is the Priorfire, but that doesn't really appear to be "secondary," more like a "more complete first burn."

Again, this is more of a learning, idea sharing, technical exploration kind of topic. Not a "how would I do this in real life" kind of thing. It's likely cost prohibitive compared to the ROI of an insert / stove.

I look forward to the discussion and hearing everyone's thoughts on this thought exercise!

Matthew
Wisconsin

 

[begreen]

It would not be easy but theoretically, with a fair amount of work, this might be possible. It would take a lot of reconfiguring and experimentation. This probably would void the home insurance policy.

Secondary combustion requires precise control of both the primary and seconday air feeding the fire. This would require sealed doors on the fireplace to start with a method of supplying controlled, primary air. Then adding a baffle and regulated, secondary air distribution system that introduces air at the right location, using draft to pull the air into the manifold as primary air is reduced.
All of this would need to be done while maintaining good control over the fire. In a large fireplace with many cubic ft. of fuel potential, this could be a major challenge.

 

[Todd]

You would also need to insulate that firebox to get the temps up to 1100 degrees that is needed for secondary combustion.

A long time ago I tinkered with my masonry fireplace by installing air tight doors, redirecting outside air into the firebox via the clean out, adding more fire bricks and installing a rough baffle out of some high temp ceramic board. I never used secondary air but it was more efficient than the original fireplace.

In the end I removed the whole metal heat form that ended up being rusted out, had a mason redo the bricks and installed a wood stove.

 

[bigealta]

Yup Woodstove or insert is the answer

 

[begreen]

Yes, the solution has already been refined, tested, and enabled in a good EPA insert and stoves.

 

[Nordicbynature]

It would not be easy but theoretically, with a fair amount of work, this might be possible. It would take a lot of reconfiguring and experimentation. This probably would void the home insurance policy.

Secondary combustion requires precise control of both the primary and seconday air feeding the fire. This would require sealed doors on the fireplace to start with a method of supplying controlled, primary air. Then adding a baffle and regulated, secondary air distribution system that introduces air at the right location, using draft to pull the air into the manifold as primary air is reduced.
All of this would need to be done while maintaining good control over the fire. In a large fireplace with many cubic ft. of fuel potential, this could be a major challenge.

Sounds like all the requirements that need to be done, are in fact what an insert does.

😁

 

[EbS-P]

The fireplace is a terrible starting point. One iteration before the fireplace was a a pit with a hole in the roof for smoke to escape. You can’t polish a turd. If one must I would use a baffle anmd extra firebricks for insulation with full sealed doors and a secondary air manifold fed with a very small variable speed bower.

 

[bigealta]

Well you actually can polish a turd.

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[EbS-P]

Well you actually can polish a turd.

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I missed this one! Glad to know!